Hydraulic media for low temperature operation



ltatented duty 3, i945 UNWEE fSTATEg PATEN? attain HYDRAUILHC MEDIA FQR ILQDW TEMPERA- TUBE OEERA'EIQN Theodore R. Donlan, Union, N. it, assignor, by

mesne assignments, to Standard Alcohol Company, Linden, N. it, a corporation of Delaware No Drawing. Application December 17, 19st, Serial No. iztfillll s Claims.

capacity, non-foaming and non-corrosive char-' acteristics and low volatility and convenient viscositiesover the range of temperature in which they are employed. The non-corrosive characteristics of the cooling media for use in automobile radiators are particularly important in view of the metallic frame work being fabricated from many different metals, notably, iron, copper, aluminum, zinc and lead and that with these metals in juxtaposition, and in alloy combination, in the presence of a water containing cooling medium, electrolytic corrosive effects are extremely destructive.

The alcohols have been employed as the sole or partial constituents of many low temperature hydraulic media. Alcohols in the pure state are relatively non-corrosive to metals, but when used as constituents in low temperature hydraulic media, especially in anti-freeze solutions for automobile radiators, conditions are encountered which cause the development of corrosive substances from the alcohols. Such conditions in the automobile radiator are the dilution with water and the circulation through the aqueous solution of air andexhaust gases, together with the effects of local overheating and of materials in suspension. In alcohol-containing anti-freeze solutions it has been necessary, therefore, to incor-' porate corrosion inhibiting compounds.

Advantages of the use of the lower alcohols in anti-freeze solutions are that less material is required to reduce the freezing point 01 water than the higher alcohols. Furthermore, at low temperatures the lower alcohols do not readily solidify but form a slush, that is, the composition as a whole at the normal freezing temperature of the composition does not solidify, but is a slushy composition and therefore relatively mobile. Thus. the use of the alcohols prevents damage to the radiator system as normally occurs when an essentially non-alcoholic aqueous solution freezes. The advantage, therefore, of the use of the lower alcohols is that if, through some accident, the

radiator contains too little anti-freeze compositlon for any given temperature, the radiator will nevertheless be protected fromthedamage ordinarily resulting from solidification of the cooling liquid contained therein.

In the preparation of hydraulic media suitable for use at low temperatures, it is highly desirable that the composite should contain an appreciable quantity of Water in order to impart the characteristics to the composition of good heat transfer, high heat capacity, low viscosity and nonfoaming characteristics and to have as the other main constituent a lower alcohol to efiect a substantial reduction in the freezing point and to impart slush-forming characteristics at low temperatures.

The present invention is concerned with reducing the corrosion of aqueous alcoholic anti-freeze hydraulic media by incorporating therein a small quantity of a compound of the type of lecithin and cephalin. Such compounds may be used alone or in mixtures. A small quantity of a relatively high boiling water-insoluble film-forming oil such as kerosene may also be added. Lecithin and cephalin are examples of a broad class of naturally occurring highly complex derivatives of glycerol, alkamines. phosphoric and certain of the higher fatty acids. These compounds, commonly termedphosphatides, are generally suitable as anti-corrosive agents in aqueous alcoholic antifreeze solutions for the purpose of this invention; but of the group, lecithin is preferred. The inert film-forming oil may be any oil relatively insoluble in water such as hydrocarbon distillate, of distillation range between that of naphtha and a light lubricating oil. This material functions largely as a plating agent over the inner sur face of the framework and aids in this manner the anti-corrosive effect of the phosphatide material in particular cases.

The compositions of the invention are usually prepared by incorporating the phosphatide material in the alcohol or mixture of alcohols. The

composition so prepared is seldom employed as a hydraulic media but is diluted with various quantitles of water according as protection is required at the particular temperatures. To this (30110811,- trated composition, the inert film-forming oil is added. The diluted diphase mixture is the usual upon the nature of the alcohol, the lower alcohols usually requiring less of the phosphatide material than when the more viscous polyhydric alcohols such as a low molecular weight glycol or glycerol are employed. An eiiective composition consists of a mixture of 66% methyl alcohol, 33%

"isopropyl alcohol and 1% water containing 8 grams of lecithin per gallon. This is diluted with three volumes of water. This diluted diphase mixture afiords protection against freezing for a cooling system of the type of an automobile radiator to a temperature of about 5 F.

Compositions, therefore, within the scope of the invention usually contain a monohydric aliphatic alcohol having up to six carbon atoms, a low molecular weight glycol such as propylene glycol, glycerol or a mixture thereof; water; the phosphatide material; an anti-leak agent such as linseed meal when a glycol is employed; an antifoaming agent especially when a glycol is employed; sometimes a dye material and a filmiorming oil such as kerosene or a light lubricating oil. The amount of the phosphatide material added to the concentrated composition usually prepared varies between about 0.1% and 2.0% by weight of that composition.

.ln example illustrative of the invention has the following composition:

Alcohol concentrate: Per cent Methyl alcohol 66.0 Isopropyl alcohol 33.0 Water 1.0

To which is added- Lecithin, 8 gm./gal. of alcohol concentrate.

Light lubricating oil (32 seconds Saybolt vis.

@ 100 F), 76 cc./gal. of alcohol concentrate.

National Alphazurine-2G-dye, 0.04 gm./

gal.

This concentrated composition is diluted as required with water for particular usages. Thus, for protection to temperature of about 20 F. a

15% aqueous solution is prepared, and for temperatures of about 0 F. a 30% aqueous solution is Prepared.

In the preparation of concentrates according to the above type, mixtures of methyl and isopropyl alcohols may vary in ranges from 90% to 10% of methyl alcohol and from 10% to 90% f isopropyl alcohol in order to prepare mixtures of specific gravity of about 0.81. Instead of such alcohols, ethyl or any other lower aliphatic monohydric a1- cohol's, or dihydric alcohols or glycerol may be used. The alcohols which are preferable in this invention are the monohydric and polyhydric aliphatic alcohols containing up to six carbon atoms in the molecule, and of these alcohols thosecontaining from one to four carbon atoms in the molecule and particularly methyl, ethyl, propyl and isopropyl alcohols, ethylene glycol and 1-2 propylene glycol and glycerol are especially preferred. Advantages of using the glycols and glycerols are, that in addition to their low freezins points and high boiling points, they become highly viscous at low temperatures before sohdifying and that, except for the very dilute aqueous solutions, expansion at low temperature does not crack the radiator or engine block of the automobile.

A disadvantage of using certain of the alcohol compounds especially the glycols in the preparation of anti-freeze solutions, is that of imparting to the composition a tendency to leak and creep through minute solder pores and crevices. To counteract such losses of material compounds of the type of linseed meal are incorporated in the compositions. Other compounds which may be used to reduce leaks are gum gambler, tragacanth, quince seed, Irish moss and their mixtures. Other well dispersed solids may be included, such as paper pulp, aluminum or bronze, but, in general, linseed or flax seed meal are preferred because of the superior results obtained, and their clean appearance. The amounts in which these materials are incorporated in the anti-freeze composition are usually about five grams per gallon of concentrate.

The amount of water in the concentrated composition is roughly that given in the specific example, although less concentrated alcohols containing larger quantities of water may also be used.

The phosphatide material used in the present inventioncomprises derivatives of glycerol with one or two of the hydroXyl groups esterified by fatty acids and of phosphoric acid combined with a basic substance. A class of phosphatidcs particularly efiective as corrosive agents in antifreeze solutions comprises a group of monoamino, monophosphatide compounds usually esters of oleic, stearic, palmitic or other higher fatty acids with glycerophosphoric acid and choline of general formulain which A indicates a high fatty acid and R an alkyl radical. These compounds are generally incorporated in the concentrated compositions in amounts between 0.5 and 8 grams per gallon and preferably in an amount between 2 and 5 grams per gallon. Of the various compounds, lecithin itself is generally used because of its ready availability and ready solubility in alcohols.

The dye material is added in small amounts to the composition in order to impart distinctive and attractive appearance for sales purposes. Any suitable dye material may be used instead of National Alphazurine-ZG-dye as given in the specific composition which is presented merely as an illustration of the invention.

Any inert film-forming material may be employed instead of thelight lubricating oil. Usually, however, the material is a petroleum distillate having a boiling range about that of a naphtha or light lubricating oil.

In some cases it is advantageous to add to the composite buffer-acting salts suchas borax and compounds such as sodium nitrite,. disodium phthalate, etc., to impart added characteristics. These compounds are not added, however, as essential ingredients and therefore their addition is not a feature ofthe present invention.

In order to demonstrate some of the favorable properties of the compositions, tests were made on the following solutions:

1. 25% (vol.) alcohol concentrate:

Per cent Methyl alcohol 66.0 Isopropyl alcohol 33.0 Water. 1.0 75% (vol.) water. Tap water.

These compositions had freezing points of about 10 F. It is correct to state that these compositions had a freezing point of about F. be-

cause at about that temperature super cooling and latent heat elects occur and throughout the mass formation '0! small ice crystals was noticeable. v

The corrosion test applied for evaluating the anti-freeze solution is as follows:

Strips of various metals (1%" x3" 2: y were fastened to a stainless steel support and immersed in the test solution'to half their length in a suitable flask vented to the air by a long glass tube air condenser. The flask was placed in a constant temperature bath maintained, at 71 C.:.5 c. for 144 hours. The strips were carefully cleaned and weighed before and after immersion. The total loss in weight expressed in milligrams represents the amount of corrosion. The lower the corrosion loss the more desirable the solution. .Corrosion losses greater than milligrams are considered objectionable degrees of corrosion.

The following results were obtained in the corrosion test upon the following solutions:

Weight differential of strips in my.

' In the description .01 the invention as given,

embodiments have been presented merely as illustrations. Modification in the specific proportion, as well as the preferred materials may be made, and the amounts of phosphatide material and inert film-forming agent may be varied without departing from the scope of the invention. The invention should not be limited other than as defined in the appended claims.

What is claimed is:

l. A non-corrosive mixture of an aqueous solution of an alcohol containing a small quantity of lecithin and an inert film-forming hydrocarbon oil of distillation range between that of naphtha and a light lubricating distillate.

2. A non-corrosive mixture of an aqueous solution of an aliphatic alcohol containing up to 6 carbon atoms in the molecule and a small quantity of lecithinand an inert film-forming hydrocarbon oil of distillation range between that of naphtha and a. light lubricating distillate.

3. A non-corrosive mixture of an aqueous solution of a mixture of alcohols containing up to 6 carbon atoms to the molecule and a small quantity of lecithin and an inert film-forming hydrocarbon oil of distillation range between that of naphtha and a light lubricating distillate.

4. A non-corrosive aqueous solution of a mix-. ture of isopropyl and methyl alcohol and a small quantity of lecithin and a light lubricating oil.

5. A non-corrosive aqueous solution of an alcohol containing up to 6 carbon atoms in the molecule, 8 grams of lecithin for each gallon of the alcohol and cc. of a, light lubricating oil tor each gallon of the alcohol.

6. A non-corrosive aqueous solution of an alcohol containing up to 6 carbon atoms to the molecule, 0.5 to 8 grams of lecithin per gallon of the alcohol and a. light lubricating oil.

THEODORE R. DON'LAN. 

